As an American emigrant: the red cups are real, but not limited to house parties; alcohol is a lot less accessible, so the party would be more likely to have four different kinds of liqueur from peoples parents or three handles of paint cleaner; getting the cops called on an underage party is serious. Like, potentially lose your job and home serious, even if you were gone for the weekend.

It is untrue. You can go to any highschool and find giant parties happening several times a year. It happens at multiple schools, kids travel to the next school over, and they will typical be 100s of kids at these things.

Maybe it's changing with gen z but the overwhelming majority of American high schoolers in the 90s and 00s were having drinks from time to time and party.

Oh no. Wait until he finds out what frat parties really look like

Might be a thing of social circles. For middle working class in NSW, personally, I've found it's not the norm in my circles and I might say it's also not the norm for even wealthier people- but I don't rub shoulders with these crowds a lot. I'm sure it happens though.

My experience elsewhere was that underage drinking was actually the norm across any backgrounds.

Fair enough. I've lived mostly in urban areas, but, good to know things are more relaxed in rural areas. (Still not smart getting drunk though)